1. Field of the Invention
The present invention relates to 1,3-bis-(dicarboxyphenyl)-1,1,3,3-tetraphenyldisiloxane derivatives useful as raw materials of polyimide resins, as hardeners for epoxy resins, and as others. The invention also relates to processes for producing these derivatives, and processes for producing polyimide resins from these derivatives.
2. Description of Prior Art
1,3-Bis(3,4-dicarboxyphenyl)-1,1,3,3-tetramethyldisiloxane dianhydride represented by the formula ##STR1## is already known as an aromatic tetracarboxylic dianhydride containing a disiloxane linkage (J. Org. Chem., Vol 38, p. 4271 (1973)).
Properties of polyimides produced from 1,3-bis(3,4-dicarboxyphenyl)-1,1,3,3-tetramethyldisiloxane dianhydride are described on page 51 of POLYIMIDES edited by K.L. Mittal (1984, issued by Plenum Press)
Polyimides produced from aromatic tetracarboxylic dianhydrides and aromatic diamines are known as resins excellent in heat resistance.
However, polyimide resins produced from 1,3-bis(3,4-dicarboxyphenyl)-1,1,3,3-tetramethyldisiloxane dianhydride by combining with aromatic diamines suffer from the problem of lower glass transition temperatures and lower thermal decomposition temperatures than those of other polyimide resins. For example, a polyimide resin from said dianhydride and diaminodiphenyl ether exhibits a glass transition temperature of 164.degree. C. and a thermal decomposition temperture of 398.degree. C.
Such being the case, there has been demand for an aromatic tetracarboxylic dianhydride which has a disiloxane linkage in the molecule and can provide a polyimide having a higher glass transition temperature and a higher thermal decomposition temperature.